1. Field of the Invention
This invention relates generally to temperature alarm systems and more particularly to easy-to-install temperature alarm systems for enclosed spaces such as refrigerators.
2. Description of the Related Art
Temperature alarm systems have long been used to monitor temperatures in enclosed spaces where perishables are stored such as refrigerators, walk-in coolers, freezers, etc. Such systems continuously monitor the temperature in the enclosed space and generate a visual and/or audible warning if the temperature exceeds certain limits. Stores and restaurants use these systems to protect their investment in perishable inventory, e.g., meats, dairy products, etc. Should the temperature in those cases rise too high, all of the perishable inventory could be ruined. As a result, temperature alarm systems are essential for modern stores and restaurants with perishable inventory.
An example of one such temperature alarm system is the SUPCO No. 3T187 sold by Grainger of Lincolnshire, Ill. The SUPCO temperature alarms allows the temperature alarm to be set at any temperature between -60 degrees to 170 degrees F. A liquid crystal display (LCD) is coupled to a temperature sensor and displays the temperature sensed thereby. A front panel allows the user to activate the alarm as well as activate a delay circuit in the alarm. The delay circuit waits a predetermined amount of time before activating the alarm after the specified temperature threshold has been violated. If the temperature remains above the specified temperature after the delay period has expired the alarm is activated. This prevents the alarm from being activated due to transient fluctuations in the temperature due to, for example, the refrigerator door being opened. If the delay circuit is not activated, the alarm is activated immediately upon the specified temperature threshold being violated.
The SUPCO temperature alarm, as with all other known temperature alarms, requires a 120 VAC power source to operate. Typically, the alarms come with a standard 4' to 5' power cord which severely limits the locations in which the system can be mounted. In order to mount the alarm in a convenient location, it is often necessary to install additional 120 VAC wiring. This adds significantly to the overall cost of the system since a licensed electrician must usually be retained to perform the work properly. It also presents a temptation to forego the cost of an electrician and run an extension cord to the unit, thereby creating hazardous conditions due extension cords dangling from fixtures and lying on floors. Connecting a temperature alarm system to a 120 VAC power source also increases susceptibility to blown fuses and other power outages. Further, if the internal circuitry requires DC power, an expensive and bulky DC power supply must be included in the system.
Accordingly, a need remains for a temperature alarm system that is compact, reliable, inexpensive, and easy to install.